Background of the Invention
FIG. 1a is a cross sectional side view of a heating assembly 100 to attach a die 106 to a substrate 112. A heating block 102 generates heat. A heat nozzle 104 transmits heat from the heating block 102 to a die 106. The die 106 is positioned above a substrate 112. Solder bumps 110, once melted by the heat applied to the die 106 and then cooled, attach the die 106 to the substrate 112. Underfill material 108, such as epoxy resin, substantially fills the areas between the die 106 and the substrate 112.
FIG. 1b is a graph that shows the heat generated by different areas of the heating block 102. The heating block 102 generates heat in a substantially uniform manner, as shown by the graph in FIG. 1b. Heat put out at one point of the heating block's 102 surface is about equal to heat put out at another point of the heating block's 102 surface. FIG. 1c is a graph that shows the thermal conductivity of the heat nozzle 104. As shown in the graph of FIG. 1c, the thermal conductivity of the heat nozzle 104 is substantially the same from the left edge 114 of the die to the right edge 116 of the die. FIG. 1d illustrates a graph that shows the temperature of the solder bump 110 and the underfill material 108 beneath the die 106 that results from the heat generated by the heating block 102 as shown by the graph in FIG. 1b and transmitted from the heating block 102 to the die 106 by the heat nozzle 104 as shown by the graph in FIG. 1c. The graph in FIG. 1d shows that the temperature at the die 106 is lower at the left 114 and right 116 edges of the die 106, and has a higher temperature peak 118 approximately in the center.
Since heat may be exchanged between the edges 114, 116 of the die 106 and the surrounding environment, some heat at the edges of the die is dispersed, leaving the center of the die 106 hotter. Applying enough heat to ensure that the temperature near the edges 114, 116 of the die 106 is hot enough to melt the solder bumps 110 to attach the die 106 to the substrate 112 may result in a higher peak 118 temperature near the center of the die 106 that may be too high and result in overheating the underfill material 108 and causing voids in the underfill 108 to occur.